The best noob-friendly app/service I’ve found for easy conversion between Bitcoin and Fiat is Strike. You get a Lightning address with your account, and you can use that to receive zaps from nostr. In your Strike account you can choose to receive as bitcoin (and sell or withdraw later) or auto convert to fiat. Full KYC of course since it’s a regulated money service. For anything not KYC you’re gonna need that 3 hour course. 😂